In general, a container bag means an industrial sack for use in transportation and storage of grains, powders, or the like, wherein such a container bag is fabricated using a foldable and flexible material and referred to as FIBC (flexible intermediate bulk container), big bag or bulk bag.
Since a container bag usually contains about 500 to 2,000 Kg of chemicals, minerals, grains, plastic products, cement or the like, it is often transported by a crane or a hoist forklift truck so as to be stored in a warehouse, or loaded on and transported by a truck.
Recently, as the quantity of goods transported has increased due to active internal trade, demand for container bags, which are stable at the time of being transported by a truck or a container vehicle or stacked in a warehouse and allow the efficient use of a space, has increased.
The above-mentioned container bag has a space for receiving contents, wherein the space is defined by a bottom wall, lateral walls and a cover, the bottom wall and the cover having openings for introducing contents into the container bag and discharging the contents from the container bag, respectively. In addition, the container bag has loops, which are distributed around the top ends of the lateral walls so as to allow the container bag to be transported by a transportation means, the loops being formed of a transportation rope or a belt.
Such a container bag is usually formed by weaving a natural fabric material or a synthetic resin material such as PVC (polyvinyl chloride), polypropylene and polyethylene in such a manner as to retain the external appearance as well as the strength of the container bag, and if desired, the container bag may be lined with an inside skin which is formed from a water-proof vinyl material.
Therefore, the external appearance of the container bag is easily deformable and foldable because it is formed from a flexible material, whereby it can be stored in a minimized status in volume when no content is contained therein. In addition, when contents fill the container bag for transportation, the container bag takes a form, which allows a maximum quantity of freight to be loaded within a predetermined space so as to reduce the freight transportation costs.
A cylindrical or square pillar type container bag is usually used for such a container bag. FIG. 1 shows photographs of a conventional cylindrical pillar type container bag and a conventional square pillar type container, respectively.
The cylindrical pillar type container bag has an advantage in that it can receive the largest amount of materials as compared with any other type of container bags having the same surface area. However, it has a problem in that when a plurality of such cylindrical pillar type container bags are loaded within a limited space, it is difficult to efficiently use the space because the percentage of void (empty space between bags) is very high.
Meanwhile, the square pillar type container bag is advantageous in view of the spatial usage when a plurality of container bags are loaded within a limited space on a transportation vehicle. However, when such a container bag contains contents, the vertical intermediate areas of the lateral walls are caused to be bulged out (hereinafter, to be referred to as “barreling phenomenon”) due to the self-weight of the contents, and the container bag is deformed substantially in a cylindrical shape like a cylindrical pillar type container bag, whereby the container bag occupies a large space when it is transported or stored.
Recently, automated warehouses have been largely used for storing container bags in a stacked state, wherein in such automated houses, each container bag is palletized, transported by a forklift truck, and stored on a support die, which is properly partitioned lengthwise and crosswise. However, there is a problem in that due to the barreling phenomenon, the width of the support die does not correspond with that of the container bags, whereby it is difficult to stack the container bags.
Various researches have been made in order to solve the problems caused when using conventional container bags. As a result, there has been provided a method for suppressing the barreling phenomenon by forming reinforcing areas in the vertical or crosswise direction on the container bags. With this method, although the barreling phenomenon may be suppressed to a certain extent, this method has problems in that due to the formation of the reinforcing areas, the manufacturing costs are increased, and due to the loads concentrated adjacent to the reinforcing areas, the container bags get torn.
There has been also provided a method for suppressing the barreling phenomenon by sewing partitions to inner walls laterally adjacent to the respective vertical corners of a square pillar type container bag in such a manner that each partition interconnects two adjacent inner walls. However, this method has a problem in that due to the formation of partitions, the manufacturing costs are increased. Furthermore, foreign matters occurring at the time of manufacturing the partitions are mixed with the contents received in the container bag, which may cause the rejection of products contained in the container bag. Moreover, the method has a disadvantage in that as being obstructed by the partitions, it is impossible to use a water-tight inside skin. In particular, there is a problem in that when a plurality of container bags are stacked, the lowermost container bag or bags may experience fracture at the partition-connected areas, whereby the stability is deteriorated.